Polyolefin fibers



United States Patent US. Cl. 26032.6 3 Claims ABSTRACT OF THE DISCLOSURE Improved textile fibers prepared from isotactic polypropylene resin containing from about 0.01 to about 1.0% by weight of erucamide. These fibers and fabrics prepared therefrom are characterized by having self-replenishing surface lubrication.

This invention relates to improved fibers prepared from polyolefin polymers, and more particularly to improved polypropylene fibers. The invention also pertains to fabrics Which are knitted or woven from yarns formed from the improved polypropylene fibers.

In general, fibers or filaments of polypropylene are prepared by extruding molten polypropylene or a solution of polypropylene through a die provided with numerous, downward-facing, small round openings. Such dies are known as spinnerets. The extruded polypropylene fibers may either be air dried or quenched. If solvent is present, it may be removed by evaporation carried out by passing the hot fiber through heated air. The solvent may also be removed by extruding the fiber into a bath which extracts or dissolves out the solvent. The fiber is then dried by the usual means.

Subsequent processing steps include orientation or stretching, take-up and draw-twisting of the fibers. More specifically, the fibers may be stretched and then knitted or woven as monofilament or multifilament yarn to manufacture various fabrics and finished articles such as hosiery. In many instances, the fibers are formed into yarns of the desired denier by twisting and doubling operations prior to being knitted or woven. It is also possible to combine the polypropylene fibers with other material or synthetic fibers to form different types of yarns.

The terms fiber and filaments as set forth throughout this specification and in the appended claims will be used interchangeably in their usual and acepted sense in the textile industry. It will be further understood that the term polypropylene is intended to mean normally solid, linear polymers of propylene. As described above, the preferred polypropylene polymers for the purposes of this invention are composed predominately of isotactic polypropylene. Some atactic polypropylene may be present, and broadly may constitute up to 20% or higher by weight of the polypropylene. In the preferred practice of the present invention, the polypropylene will contain less than about 8% by weight of the atactic form of polypropylene. The polypropylene will generally have an intrinsic viscosity of about 0.3 to 2 or higher.

As is well known in this art, synthetic polymer fibers as well as natural fiber surfaces are treated with lubricants during the yarn manufacturing operation as well as during the subsequent processing steps of knitting, weaving, braiding, and the like. Surface lubrication is also performed on the knitted, Woven or braided fabrics immediately preceding their use in the manufacture of garments or other finished articles. One purpose for the application of surface lubricants is to minimize the abrasion and wear of both the fibers and the various contact points on each other during the production of the fiber.

For example, it is customary for the manufacturer of the raw fiber to apply a spin finish to the fiber during or subsequent to the spinning step. Another purpose of lubrication is to facilitate the freedom of movement of the yarn itself which may, in turn, permit easy recovery to designed, preset dimensions. Surface lubrication in the case of knitted fabrics, also permits uniform retention of stitch formation through conventional procedures such as relaxation or shrinkage, or by extended fixed dimensional settings. Related advantages are obtained with woven, nonwoven and needled fabrics. In order to accomplish such results, surface lubrication has had to be applied at various stages during the conversion of the raw fibers into finished fabrics and articles. Thus, for example, surface lubrication has been used prior to the knitting or weaving step, subsequent to knitting and weaving, subsequent to final boarding, subsequent to scouring and drying subsequent to the conventional finishing bath treatment, etc.

Conventional lubricants and lubricating compositions have been employed heretofore in the spin finishing and other surface lubricating treatments as described above. Such lubricants have included, for example, mineral oils, mineral oil emulsions, ethoxylated fatty alcohols and acids, stearic acid and other fatty acids, polyethylene glycol esters, waxes, and the like.

A number of serious difiiculties have been encountered with respect to the use and application of the conventional lubricants to the surface of polypropylene fibers. To begin with, lubricants such as mineral oils or emulsion thereof cannot be employed, since they are readily absorbed by the polypropylene fibers, and cause swelling thereof. The use of one or more of the other lubricants, on the other hand, at best only serve as transitory assistance for accomplishing the lubrication objectives sought in any of the above-mentioned steps, since they are readily removed by simple washing, scouring or dry cleaning operations. This lack of durability necessitates multiple reapplications of the surface lubricant throughout the many .and varied steps required to form the yarn and then to transform the raw yarn into finished fabrics or garments. The need for multiple reapplications of the lubricant is a serious economic disadvantage as well as a source of trouble during the formation of the yarn and the fabrication of finished articles therefrom.

One object of the present invention is to avoid the difficulties encountered in the prior art with respect to furnishing surface lubrication to polypropylene fibers and to finished articles fabricated therefrom.

Another object of the present invention is to provide improved polypropylene fibers or filaments which do not require the reapplication of surface lubrication.

A further object of the present invention is to provide fabrics or finished articles from polypropylene fibers characterized by having outstanding surface lubrication which is not readily depletable.

These and other objects of the present invention will become apparent from the ensuing description and illustrative embodiments.

In accordance with the present invention it has now been found that durable, self-replenishing, surface lubricity can be imparted to a polypropylene fiber or filament by incorporating an amide or a mixture of amides of higher fatty acids into the polypropylene resin feed material. The term amide of a higher fatty acid is intended to apply to amides of saturated and unsaturated monocarboxylic acids, and particularly those having from 10 to 22 carbon atoms, preferably 16 to 22 carbon atoms, per molecule. Such acids are found as free acids or their glycerides in fatty oils. Examples of suitable amides for the present purposes include lauramide, stearamide, oleamide, erucamide, elaidamide, linoleamide behenamide, palmitamide, N,N -ethylene-bis-oleamide, decanamide, and the like as well as mixtures thereof. It will be understood that commercially available amides or amide mixtures may be eifectively employed in the present invention.

The amount of fatty acid amide employed in conjunction with the polypropylene may vary over a rather wide range. In general, however, the amount of fatty acid amide employed will range from about 0.01 to 1% by weight, based on the weight of the polypropylene. Preferably about 0.01 to 0.3% by weight of the fatty acid amide is utilized to achieve the desired results.

Although the present invention has been discussed above and will be illustrated below in connection with polypropylene consisting predominantly of isotatic polypropylene, it will be understood that similar or related polymers or polymer components may also be used as the starting material. Such other polymeric materials include copolymers of polypropylene, mixtures of polypropylene and other polymers, mixed polymers of polypropylene, as well as poly(4-methyl)pentene polymers.

The polypropylene-fatty acid amide compositions may be prepared by any method for obtaining a uniform mixture for extrusion into the polypropylene filaments. This can be accomplished by the use of such methods as the addition of the amide as a solid, in solution in an inert solvent, or as a slurry in water or other media which are nonsolvent to the polypropylene, which may be in the form of pellets, dry fluff or molding powder. The resulting admixture is then dried and tumbled. The fatty acid amide can also be incorporated into the polypropylene either during polymerization or subsequently thereto such as by melt blending in any conventional equipment employed for polymer compounding such as a Banbury mixer, intensive mixers, Henschel mixers, plasticators, and the like. It is also possible to prepare a concentrate of the amide in the polypropylene by one of the aforedescribed methods, and then blend the concentrate with polypropylene pellets, dry fluff or molding powder by tumbling, Banbury mixing, or other suitable means. It is also possible to have certain conventional additives such as antioxidants, heat and light stabilizers, antistatic compounds, dyes, pigments and the like present in the polypropylene feed resin.

The dispersion of the fatty acid amide in the polypropylene has been found to result in a sustained lubrication of the polypropylene fiber or filament surface. The fatty acid amides appear to be somewhat incompatible with the polypropylene and, consequently, there is a substantially continuous exudation or sweating-out of the amide from the internal or inner portion to the surface of the polypropylene filament or fiber. The presence of the fatty acid amide in the interior part of the filament is somewhat analogous to an internal reservoir which supplies a substantially continuous flow of lubricant to the surface and thereby provides a self-replenishing surface lubricant.

It was further found that when amides are incorporated in the polypropylene the lubricity of the filament or fiber surface is maintained over a comparatively long period of time. Consequently, the multiplicity of external surface lubricating treatments heretofore required could be eliminated without encountering any untoward results. Various problems which have developed from time to time in fiber production and in the manufacture of fabrics therefrom as a result of insufficient or nondurable surface lubrication were avoided. The use of the fatty acid amides also resulted in overall economic advantages over the prior art lubrication procedures. Although all or substantially all of the previous external lubrication treatment steps could be omitted by the practice of this invention, in some instances the application of an external lubricant is maintained. The use of the fatty acid amides, as described above, eliminates the majority of the subsequent external lubrication treatments as well as the requirement that the place of application be carefully selected in order to avoid a prolonged absence of surface lubrication at any point in the process of converting the raw fiber into finished fabric.

As previously mentioned, surface lubrication of the fibers is also important even after garments or other finished articles have been fabricated therefrom. The lubrication permits free motion of the yarn in the fabricated articles which increases the ease in recovery to the original dimensions. Furthermore, it should be noted that the enhanced lubrication of the fiber surface resulting from the practice of this invention minimizes excessive heat generation during the sewing operation and at the same time minimizes the problems caused when the needle is caught on the fiber surface. Finally, the improved polypropylene fibers of this invention will not be deprived of their lubricity simply by subjecting the fabricated garment to a limited number of dry cleaning treatments or washings.

The invention will be more fully understood by reference to the following illustrative embodiments.

EXAMPLE I Run A.Approximately 0.1% by weight of erucamide was blended with polypropylene resin having an isotactic content of 95.5% and then compounded with color pigments. The resulting blend was extruded in conventional melt extrusion equipment to form 15 denier monofilament and 40 denier multifilament yarns. The conventional step of orienting the yarns was accomplished using standard drawing equipment.

Run B.The same procedure of Run A was employed with the exception that no erucamide was blended into the polypropylene resin.

EXAMPLE II A first set of several dozen womens seamless hosiery were knit on a 400 single needle knitting machine. A l5-l-0.25 Z turns polypropylene yarn was used for the leg fabric, while a 4010-0.5 S turns yarn was used for welt fabric as Well as for the heel and toe fabric. Both of these yarns were extruded from a mass colored polymer containing 0.1% by weight erucamide, as described in Run A of Example I. After knitting, the hosiery was looped and preboarded using conventional equipment and procedures. The hosiery thus produced was not washed or scoured in any manner.

A second set of several dozen womens seamless hosiery was prepared as described above except that after preboarding the hosiery was scoured using conventional equipment and procedures.

A third set of several dozen womens seamless hosiery was also knit as described above except that the polypropylene resin used to extrude the yarn contained no erucamide (Run B of Example I). The resulting hosiery was looped and preboarded using conventional equipment and procedures. The hosiery was then scoured, and lubricant finishes were applied in accordancewith conventional practice. Lubricant A is a complex amine-fatty acid derivative admixed with lanolin; Lubricant B is a resin wax emulsion. Both of these compositions are commercially available and in common use for hosiery finishing.

The above described three sets of hosiery were tested to determine stretch-endurability on the Frazier Hosiery Testing Machine utilizing the present improved model of the machine originally built for the National Bureau of Standards. This is the standard test in the field, and the machine as well as the exact method employed are described in deteail by Schiefer et al., US. Bureau of Standards Journal of Research, 12, No. 5, pp. 54349, Research Paper RP 679 (1934). In this test the hosiery is first Washed by hand and air dried. The hosiery is then placed on the machine at a length between the heel and garter clasp governed by the overall flat measurement of the hose. The welt, shadow welt and knee portion of the boot are then repeatedly distended from a circumference of 12.5 inches to 22.5 inches. The hosiery was flexed until failure occurred. In accordance with the established standard, 1500 cycles is considered satisfactory stretch- On repeated launderings both in laboratory and in wear tests, the hosiery knitted from the yarns containing erucamide continued to show the same remarkable increase in flex lifedemonstrated above.

The above data show that the average number of fiexures for the hosiery prepared from fibers of the erucamide containing polypropylene resin was considerably higher than that obtained by use of the conventional external application of surface lubrication. Moreover, the

hosiery prepared by practicing the present invention results in average flexural values which far exceed the 1500 minimum established in this field. Since convention lubrication treatments did not result in hosiery meeting the minimum values, the importance of the present invention is readily apparent. Equally satisfactory results were obtained with full fashioned womens hosiery.

The improved polypropylene fibers and filaments of this invention may be employed to produce a wide variety of difierent types of fabrics, including both apparel and industrial textile products. Specific examples of these products include hosiery, lingerie, suitings, shirtin-gs, dress and blouse fabrics, and the like.

Although it is preferred to fabricate the finished fabrics or articles, e.g., hosiery, entirely from polypropylene fibers, mixtures of polypropylene fibers with other natural or synthetic fibers. The natural fibers include silk, wool and cotton; whereas the other synthetic fibers include nylon, Dacron, Acrilan, etc.

While particular embodiments of the present invention have been shown above, it will be understood that the invention is obviously subject to variations and modifications without departing from its broadest aspects.

We claim:

1. An improved textile fiber prepared from isotactic polypropylene resin containing about 0.01 to 1.0% by weight of erucamide, said fiber being characterized by having self-replenishing surface lubrication.

2. A textile fabric comprised of improved polypropylene fibers provided with sustained surface lubrication, said fibers being prepared from isotactic polypropylene resin having dispersed therein from about 0.01 to 1.0% by weight of erucamide.

3. A stocking prepared from the improved polypropylene fibers of claim 1.

References Cited UNITED STATES PATENTS 2,938,879 5/1960 Mock et al. 3,107,228 10/1963 Cappuccio et al. 3,141,872 7/1964 Natta et a1. 260-93.7 3,176,021 3/ 1965 Volungis et al.

FOREIGN PATENTS 867,280 5/1961 Great Britain.

ALLAN LIEBERMAN, Primary Examiner. 

